<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>

<body>

</body>
<script>
    function Person() {
        alert(this);
    }
    Person(); //this指向window

    function Student() {

    }
    Student.a = Person;
    Student.a(); //this指向student

    var json = {
        a: Person
    }
    json.a(); //this指向json

    //改变指向
    Person.call(json);
    Person.apply(Student);
</script>

</html>